Prior art defines US2010/0024844(A1) entitled “Warewasher with water energy recovery system” that discloses a warewash machine including a housing at least in part defining a chamber for cleaning wares. A sump collects hot cleaning water that is recirculated in the chamber during cleaning. A drain line is for draining cleaning water from the sump. A fresh water input system includes at least a hot water input that receives hot water from a hot water source and a cold water input that receives cold water from a cold water source. The fresh water input system has a common input line in communication with the hot water input and the cold water input. A cold water input valve is for controlling input of cold water into the common input line. A hot water input valve is for controlling input of hot water into the common input line. The drain line and the common input line are arranged in a heat exchange relationship to enable heat from cleaning water traveling through the drain line to enable transfer of heat to water traveling through the common input line. A temperature sensor arrangement is associated with the drain line for determining temperature of the cleaning water traveling through the drain line. A controller receives input from the temperature sensor arrangement and is operable to control the cold water input valve and the hot water input valve such that, during a draining operation, if cleaning water traveling through the drain line is above a preselected temperature, the controller opens the cold water input valve to allow water from the cold water source to enter the common input line.
The system of '844 is insufficient since it is related only to devices having multiple cycles of water heating.
Thus, first it would be advantageous to apply drain water heat reuse also in devices operating only in a single water heating cycle.
Prior art also discloses a heat exchanger, which is a device used to transfer heat between one or more fluids. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air [source: Wikipedia].
There exist different concepts of waste heat recovery units or in particular drain water heat recovery unit. Such units may be recuperators, heat pumps, run around coils and many more.
A publication of WO2013143576, entitled “Washing machine and method of operating a washing machine” discloses that in a washing machine comprising a washing tub (10) for accommodating articles to be cleaned, a water-softening device comprising an ion exchanger (30) through which fresh water can be fed before being passed to the washing tub (10), and a drain line (22; 42) for removing water from the tub (10), it is suggested that the dishwasher further comprises means (32, 34, 36; 48; 54) for providing for an indirect heat-exchange between said ion exchanger (30) and said drain line (22; 42). Further, a method of operating a washing machine is suggested, which method comprises: (A) passing water via a water-softening device comprising an ion exchanger to a washing tub; (B) heating water that is passed to the washing tub either before or after it enters the washing tub; (C) removing heated water from the washing tub; and (D) providing for an indirect heat-exchange between heated water which has been removed from the washing tub and water that is passed to the washing tub via the water-softening device.
A drawback of this system is that drain water heat present after the last operating cycle of the dishwasher is lost.
Therefore, secondly it would be advantageous to apply drain water heat reuse also in case of a final drain of a given operating cycle of a machine such as a dishwasher.
The aim of the development of the present invention is an improved and cost effective a system and method for reducing energy consumption by a medium heating device.